Transcription translation

Gene Expression - Cookbook Analogy

The Molecular Basis of Heredity

The central dogma of molecular biology is that information is
transferred from DNA to RNA to protein.

When a gene
(segment) of DNA
code is used to build
a protein, scientists
say that gene has
been expressed.

Transcription

Translation

DNA to RNA = Transcription

RNA to Protein = Translation

On pg. 92 Fill in the blanks with the image

Turn to page 93: Types of RNA

All three major forms of RNA—mRNA, tRNA, and rRNA—are
involved in the process of gene expression.

Turn to page 93

RNA Synthesis: Transcription

In transcription, segments of DNA serve as templates to
produce complementary mRNA molecules.

A=U

RNA Synthesis: Transcription

Transcription is catalyzed
by RNA polymerase

● It unzips the DNA

strands

● Then joins together the

RNA nucleotides that

are complementaryto
the DNA template strand

● Transcription follows the

same base-pairing rules
as DNA, except that
uracil substitutes for
thymine

Turn to pg. 94
Transcribe the RNA (don’t do the amino
acids yet)

Check your answers

A U G G U A C C U U A A U G A

A A G U U A C C A G A U C C C

U G U A A A G U C U G G C A G

Translation: Making of the proteins

In order to translate, you need a Start
Codon. AUG

The Genetic Code: Codons

▪ The genetic code is read in three-letter groupings called

codons.

▪ A codon is a group of three nucleotide bases in

messenger RNA that specifies a particular amino acid.

AUG

AAC

UCU

Translation: The Polypeptide Assembly

As the ribosome moves down the mRNA, puts the right amino
acids in the correct order by matching the mRNA with the correct
tRNA that carries the amino acid.

How do we read the code for the Codons?

What
amino
acid does
the codon
G C A
specify?

Turn and Talk: Reading Codons

What
amino
acid does
the codon
C U A
specify?

Reading Codons

C U A

On the wheel,
start on inside
and work
outward.

When we do this,
we find that CUA
specifies for the
amino acid
Leucine (Leu)

Start and Stop Codons

The methionine codon AUG serves as the “start” codon for
protein synthesis. There are three “stop” codons.

AUG = “start” codon
AUG = methionine

UAA, UAG,
and UGA
are “stop” codons

pg. 94
now translate the mRNA

A U G G U A C C U U A A U G A

A A G U U A C C A G A U C C C

U G U A A A G U C U G G C A G

Genetic Code Table and Wheel

Important!!
You only use these with mRNA,
not DNA or tRNA

pg. 94
now translate the mRNA

A U G G U A C C U U A A U G A

A A G U U A C C A G A U C C C

U G U A A A G U C U G G C A G

Met

Val

Pro STOP STOP

Lys

Leu

Pro Asp

Pro

Cyc

Lys

Val Trp

Gln

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